Recently, processes for producing a styrenic polymer having the syndiotactic configuration in the presence of a catalyst comprising a transition metal compound, particularly a titanium compound, and methylaluminoxane as the main components have been proposed (the specifications of Japanese Patent Application Laid-Open No. Showa 62(1987)-187708 and other like applications).
In order to produce a styrenic polymer having the syndiotactic configuration efficiently in the above processes without the aluminoxane which is expensive and used in a large amount, processes using a coordinated complex compound comprising an anion having a plurality of groups bonded to a metal and a cation have also been proposed (the specifications of Japanese Patent Application Laid-Open Nos. Heisei 2(1990)-415573 and Heisei 2(1990)-415574 and other like applications).
To polymerize a monomer in the presence of the above catalysts, processes for producing high performance polymers with a high yield in the presence of catalysts formed by reaction of a transition metal compound with a reaction product of an organoaluminum compound with water or a compound which can form an ionic complex by reaction with the transition metal compound are already disclosed.
However, these catalysts cannot always exhibit a sufficient catalytic activity, and large amounts of metals are often left remaining in the formed polymer to cause adverse effects on physical and other properties of the polymer. As the result, complicated facilities are required for the after-treatment of the polymer.
The above processes have other problems in that the catalytic activity is decreased to increase the contents of residual metals in the formed polymer, and decomposition products of the alkylaluminum are left remaining in the polymer, and that, when the temperature of polymerization is increased, the catalytic activity is decreased to increase the contents of residual metals in the formed polymer.
Accordingly, development of a polymerization catalyst which can achieve decrease in the contents of residual metals in obtained polymers, simplification of the process for producing polymers, and reduction of the production cost of polymers has been desired. Development of a polymerization catalyst which provides a polymer having a higher molecular weight than that of polymers obtained in the presence of conventional catalysts has also been desired.